Scientists have now confirmed that the long reign of dinosaurs was ended by a climate change before and after a big asteroid slammed into Earth.
The impact at Chicxulub in modern-day Mexico certainly contributed to the disappearance of the dinosaurs, but was by no means the sole cause, a team concluded in a study published in Nature Communications.
Ten of the 24 species which disappeared at one Antarctic island did so long before the comet or an asteroid hit the planet some 66m years ago.
The other 14 disappeared in a second extinction wave that started with the impact contributing to the second-biggest mass extinction in history.
The dinosaurs’ demise, according to US-based researchers in the new paper, was caused by two periods of global warming – the first sparked by monster volcanic eruptions in what is India today, and the second by the asteroid’s impact.
“We find that the end-Cretaceous mass extinction was caused by a combination of the volcanism and asteroid impact, delivering a theoretical ‘one-two punch’,” said study co-author Sierra Petersen of the University of Michigan, using boxing terminology.
The team analysed the chemical composition of 29 fossilised shells from the period, to compile a brand-new temperature record spanning 3.5m years over the end of the Cretaceous and beginning of the Palaeogene eras.
The shells lived 65.5m to 69m years ago in a shallow coastal delta near the northern tip of the Antarctic peninsula, said a statement from the university.
At the time, the now ice-covered continent was likely covered by coniferous forest.
Scientists now warn us that burning fossil fuels for energy will eventually cause a new mass extinction in the future, and this time it will be us.
source - theguardian.com